1. Field of the Invention
The present invention relates to a legged robot that performs motion by changing a joint angle and its control method.
2. Description of Related Art
Various techniques have been proposed for generating a walking trajectory of a legged walking robot. As one technique of generating a walking trajectory of a legged walking robot, a technique of generating walking motion of a robot by designating the vertical movement of the center of gravity to thereby calculate an optimum landing position with no falling down in real time is known (e.g. Japanese Unexamined Patent Application Publication Nos. 2006-212736 and 2004-167676). In this description, the term “trajectory” refers to data that describes a change in position over time.
The technique of the related art as described in Japanese Unexamined Patent Application Publication No. 2006-212736, for example, designates the landing positions of the foot for a plurality of number of steps in advance and generates a trajectory so as to reach the designated landing positions with regard to trajectory data of the next motion interval to be given to a robot. The technique then acquires a trajectory for the first step from the trajectory for a plurality of number of steps and supplies it to the robot. In the generation of the trajectory, the trajectory of the center of gravity is generated so that a ZMP (zero moment point) that is calculated by a ZMP equation coincides with a target ZMP. The trajectory data of one step designates condition of the translational velocity of the center of gravity as boundary condition for each step so that the trajectory is continuous with respect to the current state (a center-of-gravity position, a travel velocity etc.) of the robot.
However, the related art described in Japanese Unexamined Patent Application Publication No. 2006-212736 or the like discloses nothing about the way of designating velocity boundary condition in one-step interval for various walking and running patterns. The velocity boundary condition should be such that the center of gravity position and the target ZMP position (grounding position) that are obtained as a result of solving the ZMP equation under the designated velocity boundary condition are realizable.
For example, in the case of performing on-the-spot stepping motion, it is not always clear what value should be preset for the velocity condition of the center of gravity, and therefore only the previously regulated limited pattern can be realized. Further, the related art discloses nothing about the configuration that enables generation of walking and running trajectories in real time with the use of a technique of determining the velocity boundary condition of a one-step trajectory.
As described in the foregoing, it has been difficult to generate trajectory data by setting adequate velocity boundary condition in advance for various walking and running patterns, and the related art can only realize the previously regulated limited pattern.